Heater control problem from a newbie help!!

[GMC"ER]

Hello I have only posted on here a few times I am now starting on my 69 GMC stepside. I will start from the beginning when I got the truck the controls were broken and a mess the blower was hooked up straight with a toggle switch... it all came out! Now I have installed a complete new heater control system w/o air by the way, new heater harness, new cables, so everything is new I did not replace the speed resistor I checked it and the coil springs were good and I also checked it with a test light to see if power was in fact going through and it was so I installed all new parts today and nothing... I checked and double checked everything that I can think of again and again? Still no blower, I even took the wire off the blower out under the hood and run it strait to the hot post on battery and the blower run so the blower is good. The only thing that I can think of maybe I got a new heater control with a bad switch? Would the speed resister be showing a false reading and not letting the blower switch work? I don't know of anyway else to check a speed resister If it has power going through both sides and the coils are not broken would that not be right? maybe I will get another new switch and a new speed resistor and see how that goes? Any advice? Does this sound right, have I missed something? Any help would be great, thanks Robert DeBord

[Lee H]

Robert, welcome to the board. There's a gold mine of info and some very knowledgeable folks here. I'd start at the blower motor with a test light and work backwards until power is found. You could also work the other way until power is lost. Good old detective work will solve your problem. Lee
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[Longhorn Man]

I would start at the resister with that test light. Power in? Power out?
You'll know if you need to head north, head south, or head to the parts store for a resistor.

[VetteVet]

Hi and welcome from Michigan as well.
Here are a couple of diagrams that show the path of the heater switch feed wire from the fuse panel. It's a 14 gauge brown wire shown by the red arrows.

Here is the wire at the fuse panel.



Here is where it ends at the heater switch.



If you have power at the fuse then you should have power at the switch. If the previous owner cut the brown wire and switched it directly to the orange wire then you will have to redirect the brown wire back to the heater switch as well as the orange wire.

[GMC"ER]

Thanks guys for the help and routing of wire diagram. I tested my wiring and I have no brown wire that I can see coming from anywhere out of the fuse box or harness. I have a mess under the dash the previous owner added a tach, gauges and a CD player and cut the dash so I really have a project! Also if 10 inches of wire was needed he just used a big long piece and crammed it up under the dash I have had a time just trying to sort out what everything is and shorting it down and adding proper connections and removing the "duct tape" covered splices, Oh what a wonderful time under there!! Anyway I cannot find any brown wire coming out of the fuse box apparently it has been cut out I don't know I guess it comes out the back of the fuse box and continues on from there? I have no wire going to the heater blower switch at all. But I do have a new wiring harness with orange,blue and yellow wire coming out of switch and running to resistor then an orange wire going out fire wall to blower. I ran a hot wire out of the fuse box and done a temporary splice on the wire going from resistor to blower to see if I had power running back through the resistor and I did so I think the switch out is OK and the blower would run at one speed. My problem I think from the diagram is that I do not have a brown(hot) wire going to blower switch so no power, right? Can I just run a jumper off of the heater fuse over to the switch to get power? Is there a terminal on the switch to hook it to? I am not the worlds best at wiring so I hate to sound so stupid with the questions. If I remember right the harness that plugs into the switch only has 3 wires and the switch has 4 terminals how do I hook to it and where? Again sorry for the simple questions I just don't do wiring that well. Somebody please tell me if a jumper wire is the way to go about this or if this is even right? Thanks Robert DeBord "A NEWBIE CONFUSED"

[VetteVet]

You are on the right track and if you have no brown wire from the ignition switch then you must not have any accessories and the heater switch will not work. If you have the brown wire from the ignition switch to the fuse panel but you have no brown wire from the panel to the heater switch then the same thing. IOW no power to the heater switch. AS you have found out , if you jump power to the heater switch you can make it work. You can run a wire from the heater switch fuse 10 amps, to the heater switch and it should work.

The harness will plug into the heater switch and the terminal that's left is the one the jumper wire will go to. It should be common to the rest of the terminals as you switch between them.

[GMC"ER]

Thanks guys, VetteVet I took a temporary jumper wire from the heater fuse and ran to the terminal that was on harness switch and bingo! the fan switch worked! I am going to look for that brown wire lost under the dash may have to take fuse panel off and look at the back and trace it down that way never know it may have been changed out over the years for a different color for some reason? If no wire is found I will just ran a fused link wire to the switch from the heater fuse in panel box I always like to put a in line fuse for safety. Thanks for the help guys, Robert